To generate map data for use by navigation devices, such as Portable Navigation Devices (PNDs), it is desirable to determine the number of lanes into which roads are divided (hereinafter referred to as “lane count”). The navigation device is then able to provide accurate information and instructions concerning a route being driven, such as a display of the lane count. The determination of the lane count can be carried out manually. However, such manual identification is slow and involves significant labour costs.
To reduce the time and amount of manual labour required in determining lane count, a method for automatically identifying the lane count is used. One such method analyses data, such as position data, collected from Tom Tom navigation devices in vehicles as the vehicles travel the road (hereinafter referred to as “probe data”). Below is a table of the results of such a method applied to roads where the number of lanes is known.
TABLE 1Count of outRefOut2345Grand Total23283273535613489103719314173341073114775241419528513841626Grand Total390721347595397339
The table shows the number of roads automatically identified as having a lane count of 2, 3, 4 or 5 from the probe data, denoted “out”, against a reference value, denoted “Ref”. As can be seen, for the 3907 roads having two lanes, the automatic analysis of the probe data only identifies 3283 roads as having two lanes; the automatic analysis misidentifying other two lane roads as having more lanes. Similar results are obtained for roads having other lane counts. The automatic identification of lane count from probe data is particularly poor for roads with five lanes.
It is desirable to improve the accuracy of the automated lane counting.